1. Field of the Invention
The present invention relates to a touch panel-equipped display device, and in particular to a touch panel-equipped display device having a static capacitance coupling type touch panel.
2. Description of the Related Art
As major types of touch panels, there are known a type for detecting an optical change and a type for detecting change in electrical characteristic. As a type for detecting change in electrical characteristic, a static capacitance coupling type is known (see Japanese Patent Laid-open Publication No. 2008-65748 and Japanese Patent Laid-open Publication No. 2009-015489).
According to a conventional static capacitance coupling type touch panel, disclosed in the above-described Japanese Patent Laid-open Publication No. 2008-65748 and Japanese Patent Laid-open Publication No. 2009-015489, a plurality of electrodes (X electrodes) and a plurality of electrodes (Y electrodes) are formed on different electrically conductive layers (a lower layer and an upper layer), respectively, via an insulating film. For the above described electrode structure, the insulating film and a protective film formed on an electrode on the upper layer are distorted due to the electrode on the upper layer. In addition, as the optical path length for reflected light is different between the lower layer and the upper layer, a color difference is caused between an electrode on the lower layer (e.g., the X electrode) and an electrode (e.g., the Y electrode) on the upper layer, which causes an electrode pattern of the electrodes on the upper and lower layers to appear to become noticeable. An electrode pattern having been appeared to be noticeable, as described above, will deteriorate optical characteristic, resulting in deterioration in characteristic of the display device with a touch panel mounted therein.
In view of the above, the present applicant has proposed a touch panel adopting a new electrode structure, and already filed a patent application therefor (U.S. patent application Ser. No. 12/427,878).
FIGS. 6 to 8 are diagrams related to an electrostatic capacitance type touch panel for which the present applicant has already filed a patent application. In particular, FIG. 6 is a plan view showing an electrode pattern of a touch panel; FIG. 7 is a cross sectional view showing a cross sectional structure along the line VII-VII in FIG. 6; and FIG. 8 is a cross sectional view showing a cross sectional structure along the line VIII-VIII in FIG. 6.
In the touch panel shown in FIGS. 6 to 8, an electrode 1X has a first portion 1a and a second portion 1b. The first portion 1a is formed on a layer different from the layer on which electrode 2Y is formed, so as to intersect the electrode 2Y. The second portion 1b is formed on the same layer as that where the electrode 2Y is formed, but separated from the electrode 2Y. The first portion 1a is connected to the second portion 1b in a contact hole 12a formed on an insulating film 12 between the first portion 1a and the electrode 2Y. For this electrode structure, a protective film 13 can be formed having a consistent surface so that the distortion of the protective film 13 can be suppressed, and therefore, appearance of an electrode pattern due to color difference due to distortion of the protective film 13 can be suppressed. As a result, as deterioration of optical characteristic due to an appeared electrode pattern can be suppressed, deterioration in characteristic of a display device with the touch panel mounted therein can be suppressed.
Further, as a portion with color difference caused can be minimized to the first portion 1a of the electrode 1X alone, an appeared electrode pattern due to color difference due to difference in an optical path length can be suppressed. As a result, as deterioration in optical characteristic due to an appeared electrode pattern can be suppressed, deterioration in characteristic of the display device with the touch panel 20 mounted therein can be suppressed.
Still further, when a defect is caused in the first portion 1a (bridge portion) formed on the upper layer, the defect can be repaired by carrying out again a process for forming the first portion 1a. That is, deterioration in optical characteristic due to an appeared electrode pattern can be suppressed so that processability can be improved.
However, in the touch panel shown in FIGS. 6 to 8, formation of an upper layer electrode (the first portion 1a of the electrode 1X) on the insulating film 12 is inefficient in view of process, material, and costs as requiring material and process similar to those required in formation of a lower layer electrode (the second portion of the electrode 1X and the electrode 1Y) under the insulating film 12, although the area for formation is very small. Such inefficiency needs to be addressed, or otherwise causing increase of the cost of a display device with the touch panel mounted therein.
In view of the above, the present inventor takes notice of the wiring electrically connected to the matrix electrodes (electrodes 1X and 1Y) in achieving the present invention.